This invention relates to the centrifuge field, and specifically to the problem of removing separate layers of material from their containers after centrifugation.
Various techniques have been used for separately extracting from a centrifuge tube the materials which have been separated into layers. For example, an aspiration method may be used, in which material from the upper end of the tube is withdrawn by a pipette; or a displacement method may be used, in which an immiscible high density liquid is injected through a hole pierced in the bottom of the tube to sequentially "float out" separate layers containing the desired samples.
The aspiration and displacement techniques are often deficient, in that they tend to re-mix the separated layers, and the displacement technique usually requires piercing of the tube wall.
Another separation technique is cutting through the tube, or pinching it off at the desired location(s).
The cutting technique has the inherent problem of leakage, i.e., material in the tube tends to escape along the surface of the cutting blade. Heretofore, the primary solution of the leakage problem has been the use of rubber grommets, or seals, engaging the opposite sides of the blade.
The use of seals riding against the blade has certain deficiencies, e.g., problems in cleaning the seals after cutting, contamination of the sample by its contact with the seals, and damages to the seals by the cutting blade itself.
In Wright and Wedemeyer Application Ser. No. 453,192, filed Dec. 27, 1982, and having the same assignee as the present application, "Pregrooved Centrifuge Tubes" are disclosed, which facilitate tube slicing by providing one or more grooves in the outer circumference of a centrifuge tube to facilitate its partitioning by slicing. In other words, the tube is sliced at one or more of the grooves, making cutting easier, and also using the groove to guide the cutting blade.
The grooved tube technique is somewhat limited in usefulness by the fact that the groove locations must be determined before the centrifugal separation, as grooving the tube after centrifugation, while technically possible, is economically infeasible.
The present invention is intended to solve the problems discussed above.